Cloud Computing (CC) is an Internet based computing technology having shared scalable infrastructure that can be used as service by users. Simply CC can be referred as hardware & software deliverable using Internet that is also as a service. Regardless of its popularity large organizations, enterprises are reluctant to move on cloud computing due to its security issues, especially user's data security. Organizations have expressed concern over data security as their confidential and sensitive data needs to be stored by service provider at any location globally, that's why security can't be compromised at all. CC has different security issues at different levels like software security, platform security, infrastructure security, etc.